Shift Interrupt method for a Marine Propulsion System

ABSTRACT

Device designed to retrofit a marine propulsion system from an old shift interrupt control strategy with a new shift interrupt control strategy to improve shifting performance, reliability, and ease of use. Can also be used on new systems.

TECHNOLOGY AREA

Marine Engines

US classes 440/1, 440/2, 477/107, 477/109

REFERENCES

U.S. Pat. No. 6,942,530—Control strategy based on boat speed and engine temperature to facilitate shift.

U.S. Pat. No. 8,961,246—Control strategy based upon position thresholds. Uses a potentiometer and Analog to Digital Converter in conjunction with a micro controller.

U.S. Pat. No. 7,836,787—Shift system for boat propulsion unit.

U.S. Pat. No. 9,422,047—Systems and methods for facilitating shift changes in marine propulsion devices. Uses idle air control and timing. Uses a potentiometer and Analog to Digital Converter in conjunction with a micro controller.

U.S. Pat. No. 9,493,220—Uses a potentiometer and Analog to Digital Converter in conjunction with a micro controller.

U.S. Pat. No. 9,043,058—Uses a potentiometer and Analog to Digital Converter in conjunction with a micro controller.

Problems with Current Methods

Older systems interrupt the coil to kill the engine briefly enough to allow the Dog clutch to release and allow a neutral gear to be achieved. These systems use a micro switch that is activated by tension exerted on the lower shift cable. This tension occurs when the dog clutch is transitioning and trying to come out of gear into neutral. This traditional method can stretch the shift cable over time and eventually lead to failure and require replacement of the cable. Additionally, the micro switches wear out and start activating erroneously and are unreliable. These traditional micro switch methods do not interrupt the engine when transitioning from neutral into gear which causes grinding and hard shifting.

How the Problem is Solved

With my solution, shifting is determined by the placement of magnets. Once these magnets are aligned properly, shifting is reliable and consistent.

With this invention an interrupt can occur when transitioning from neutral into gear, which reduces grinding and helps ensure a smooth shift.

There are less components to wear-out since the device is electronic and uses hall sensors and, therefore, has less moving parts.

Novelty Features and Benefits

As in all the other patents I have researched, and some are referenced above, all shift interrupt commands are determined by a control circuit that monitors the position of a potentiometer or the activation of a switch. With other methods a microprocessor/computer uses that information to determine when and how long to initiate a shift interrupt. My device is the only method that uses Hall Sensors and magnets as “interrupt trigger points”. The placement and pole orientation of these magnets determine when to send a shift interrupt, it does this directly, and is adjustable (by moving magnets) by the boat operator or mechanic. The width of these magnets can be increased to lengthen the time of the shift interrupt. The control circuit is also novel in that it does not use a computer or micro-controller. The control circuit is simply a RC time circuit to control the duration of the interrupt and activates a relay (or solid state similar or equivalent).

DETAILED DESCRIPTION

The Hall Effect sensor latch (as referenced in the data sheet AH276) “toggles” its output like a “flip flop circuit” based upon the direction of a passing magnetic field. The sensor assembly has two parts, the Hall Sensor and the Magnet assembly. The Magnets can be moved to determine when the Hall is triggered and the length of time it's triggered, thus implementing a shift interrupt.

Pins 2 and 3 are the “toggle” output. When the sensor detects a Magnet passing from North to South, output 2 turns on and 3 turns off. When the Hall detects a magnet passing from South to North, output 3 turns on and 2 turns off. Or vice versa determined by the pole orientation of the magnets. Duration can be increased and can be directly proportional to the width of the magnets.

The above described sensor sends its output state to pin 2 of the circuit shown in FIG. 3.

The prototype uses a USB cable to connect between the sensor and the Monostable circuit, but any method of interconnection may be used and would be obvious to anyone with regular skill in the field of electronics. Pin 2 of the Hall sensor provides an input to the Monostable Multivibrator circuit via a coupling capacitor (“C3”). In the schematic and our prototype, the Monostable Multivibrator circuit is designed using a 555 timer chip. There are a great number of other ways to design a Monostable Multivibrator using other circuits that would be obvious to anyone having regular skill in the field of electronics.

When the input (pin 2) of the 555 is lower than ⅓ of the input voltage VCC the Monostable circuit is triggered and provides an output at pin 3, which turns on a transistor to provide power to the output relay.

The duration of time the relay stays on is determined by the RC time constant of (C1 and R1). R1 is a potentiometer and is adjustable by the user to determine the maximum interrupt duration without stalling the engine.

Advantages: Inexpensive to make. Easy to install. Adds capability to interrupt when transitioning from neutral into gear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a Simple Block Diagram

FIG. 2 is a One Shot Monostable Multi-Vibrator control circuit. The values of R and C determine the duration of the output pulse width. Time=R×C When pin 2 detects a falling edge, the circuit is triggered for the duration of time determined by the RC time constant.

FIG. 3 is a Hall Sensor Trigger Circuit. This circuit substitutes the “trigger Switch” in the One Shot schematic in FIG. 2. A passing magnetic field causes the DO output to turn on or off and is Coupled through the capacitor to trigger (pin 2) of the One Shot in FIG. 1.

FIG. 4 is an Output Relay. The output of the One Shot momentarily powers pin 2 of the relay coil. The engine coil is interrupted be either “opening” or “closing” the coil's PWR, via the COM+N.C., or COM+N.O. relay connections.

FIG. 5 is the production circuit I have designed. It is a combination of FIGS. 2,3 and 4 except it has the power supply circuit. “Hall pin 2” and “Hall pin 3” refer to Hall sensor part no: AH276

SUMMARY

I Initially designed this circuit to retrofit existing systems, such as, used in expired U.S. Pat. No. 4,753,618 or any other system utilizing a micro switch to perform a shift interrupt but may also be used in new systems. With my solution a shift interrupt is implemented and triggered directly from a Hall Sensor and a One Shot Circuit. Specifically, it interrupts the engine coil when the position of the shift cable causes the hall sensor to detect a change in the direction and/or width of the magnetic fields. Meaning, the magnets move across the Hall sensor when shifting gears. The magnets are arranged in a particular pole arrangement. A transition of magnetic poles (North to South or South to North) causes the sensor to toggle it's output and latch. Once latched to a specific output, a transition to another direction toggles and latches to another output. This output toggle state is fed directly to trigger a mono stable multivibrator circuit that has an RC time circuit that controls the time length of the interrupt. 

1. Method to input using a Hall effect sensor latch. The Hall sensor may either contain a built in latch or have an external latch circuit. Shifting is implemented only when a Hall Sensor detects a change in position and direction of passing magnets. Specifically, detects a change from North to South and activates the shift delay. A change from South to North resets the circuit ready to be triggered again by a N to S polarity, or vice versa and depending upon the pole orientation of the magnets. The width of these magnets can be increased to change the length of time of the shift interrupt.
 2. Method to control and use the information obtained from the sensor (in claim 1) to accurately control the time in which the engine coil is interrupted. The sensor directly “triggers” a One Shot Circuit (Monostable Circuit) (which then provides an output to the method in claim 3) for a duration determined by an RC Time constant adjusted via potentiometer or alternatively as described in claim
 5. 3. Method to interrupt using the specified time duration determined using the circuit in claim
 2. The positive connection to the engine coil may be interrupted via a “Normally Closed” relay, MOSFET, IGBT, or Solid State equivalent. Alternatively, the Coil may be grounded out via a “Normally Open” relay, MOSFET, IGBT or Solid State equivalent.
 4. Alternative method to supplement claim 1 if the sensor doesn't have a built in latch, a logic circuit or flip flop circuit may be used. The circuit remembers the last output state of the hall sensor.
 5. Method to Supplement claim 2 adding ability to monitor the engine RPMs and add or subtract capacitance or resistance in the RC Time circuit to change the delay interrupt time accordingly. 